The present invention relates generally to apparatus method for developing wound coils for ultimate insertion into the magnetic cores of electromagnetic devices, and in particular to apparatus for damping vertical oscillations of the wire between the flyer and coil form in coil developing devices of the wind and shed type.
In the manufacture of electric motors, and in particular the stators therefor, it is necessary to form a plurality of coils of wire for ultimate insertion into the slots of the stator. One technique for forming such coils is known as "shedder" or "wind and shed" winding, which comprises holding a stepped coil form assembly in a winding plane while turns of wire are wound thereabout by means of a flyer which rotates about the coil form. Typically, the coil form has a vertical orientation and the flyer rotates about a vertical axis which is generally parallel to the orientation of the coil form.
While turns of wire continue to be generated, at least a portion of the coil form assembly is jumped axially relative to the winding plane and to a winding turn receiving mechanism. Alternatively, the receiving mechanism and coil form assembly may rotate, or the wire dispenser and receiving mechanism may be jumped relative to the coil form assembly. When any of the above procedures are followed, however, a plurality of winding turns will be generated in substantially one given plane. As successive turns are wound onto a coil form section, previously wound turns are moved downwardly, and such turns move from the end of the coil form into the transfer and/or injection tool.
A long recognized problem inherent in the wind and shed technique for developing coils is that of wire oscillation or flutter in directions normal to the winding plane as the wire is drawn out of the rotating flyer. In order for proper development of the individual turns of the coil, it is important that the wire be wound around the coil form in a precisely located position. If the wire is oscillating, however, there is a very good chance that one of the peaks of the oscillation will occur just as the wire is being wound around the coil form, thereby causing it to be wound in interfering relation with the last previous wire turn. This will result in one turn crossing another so that proper shedding action is impaired. This problem is even more serious in the case of coil forms which have crossover steps machined in the back form for the purpose of facilitating the climbing of the wire from one step to the next when the coil form is jumped. If a high excursion of an oscillating wire catches the crossover step, it will be held on the next higher step and then crossed as the next turn is wound around the coil form on the proper step. A wire jam occurs as the coil is moved down into the transfer and/or injection tool resulting in wire breakage and necessitating stoppage of the machine.
One prior art technique for reducing the amplitude of the oscillations between the flyer and coil form is to increase the tension on the wire. The problem with this, however, is that this results in stretching of the wire thereby reducing its cross-section and current carrying capacity. Furthermore, this increased tension work hardens the wire, a situation which is generally to be avoided.
A further proposed solution to the problem of wire oscillation is the provision of a masking plate, which is positioned just beyond the end of the flyer so that it is in close proximity to the winding plane but on the same side of the winding plane as the free end of the coil form. The masking plate includes an opening through which the coil form extends as it is jumped to progressive positions as the larger coils are developed. An example of such a masking plate is disclosed in U.S. Pat. No. 3,514,837, which is owned by the assignee of the present application.
The difficulty with such a masking plate, however, is the fact that there is a portion of the flyer arm which extends below the winding plane, that is, the plane defined by the rotation of the point on the flyer arm at which the wire is discharged and wound on the coil form, and this necessitates that the masking plate be spaced from the winding plane. Even though the spacing of the masking plate from the winding plane may only be on the order of a fraction of an inch, this may be three or four wire diameters, and an oscillation amplitude of this magnitude can easily result in crossing of adjacent turns thereby causing jamming of the wire.
In order to reduce the amount of the clearance between the effective portions of the damping or masking plate in the winding plane, an interference ledge, which is preferably horseshoe in shape, is provided on the masking plate immediately adjacent the winding plane in an attempt to reduce the amplitude of the wire oscillations. Such an interference ledge is disclosed in U.S. Pat. No. 3,967,658, which is owned by the assignee of the present application.
Although the interference ledge described above is effective in reducing the amplitude of the oscillations, its effectiveness is directed primarily to those excursions of the wire out of the winding plane in a direction toward the free end of the coil form which, in the case of most winding apparatus of this type, is in the downward direction. Excursions of the wire in an upward direction, that is, toward the winding head and the larger steps of the coil form, are still a significant problem. It is believed that this is due primarily to the fact that, as the wire is fed through the flyer arm, which may be tubular in nature, it makes an abrupt turn just before the point of discharge from the flyer arm. The tendency of the wire to follow the radius of curvature established by the bend in the flyer tube or around the flyer pulley, causes it to fly above the winding plane and then return to or below the winding plane so as to form a wave in the wire above the winding plane which causes the wire to oscillate. Thus, in order to most effectively damp the oscillations of the wire, it is necessary to reduce the amplitude of the oscillations above the winding plane, rather than below the winding plane, as is done with the aforementioned masking plate with, or without, the interference ledge.
A further problem with the prior art masking plates is that they restrict access to the coil form in the event maintenance or the clearing of a wire jam is necessary.
The wire vibration dampener according to the present invention is suitable for use on a wide variety of prior art coil winding apparatus of the wind and shed variety. The following U.S. patents, which are owned by the assignee of the present application, are examples of such apparatus: U.S. Pat. Nos. 3,514,837; 3,672,040; 3,672,027; 3,765,080; and Re. 29,007. These patents are expressly incorporated by reference into the present application, as are the entire disclosures of each of them.